Word processing and office systems are primarily concerned with the generation, editing, displaying, printing and filing of documents. Those documents may include text in the case of word processing and they may include alphanumeric tables and graphics.
In addition to word processing tasks, the data processing systems may perform other tasks such as merging of forms, checking spelling through a dictionary task, spread sheet manipulation and communications. Less sophisticated systems allow only one such task to be performed at a given time. However, when a task requires little user input the keyboard remains idle. More sophisticated systems allow for multi-tasking. In such systems, an application task which requires little or no user input is performed by the system in a background mode; that is, the task does not interact with the keyboard and leaves the keyboard available to other tasks. A foreground task, on the other hand, which does require user input, interacts with the keyboard.
A common display technique for multi-tasking systems is referred to as windowing. In that technique, a document or a portion of a document being processed by the foreground task is predominantly displayed on the system display. Background documents relating to the background tasks are displayed in part so as to be perceived as being positioned below the foreground document but in partial view of the user. A background document can be moved into the foreground by positioning the display cursor over the selected background document. Only the task associated with the foreground document has access to the keyboard.
In another form of windowing, displays of documents associated with the various tasks are not overlapped. Rather, the various task windows are positioned in a side-by-side relationship.